Even as war rages, Syrian group plans for "Day After"

"Syria's future is really up to the Syrian people and they'll have to decide how to work out a new system of government if Assad goes," said a U.S. official, speaking on condition of anonymity.

"Without responsible leadership on all sides the country, post-Assad, could slide deeper into civil strife, but there's nothing inevitable about this outcome."

U.S. Defense Secretary Leon Panetta has said that Syria's armed forces should stay intact if Assad leaves power. That is in contrast to Iraq, where the United States disbanded the army, a step that inadvertently stoked the insurgency there.

U.S. President Barack Obama's administration has focused on providing non-lethal help such as humanitarian aid and communications equipment to the Syrian opposition, but stopped short of arming the rebels.

Critics of that policy say arming the opposition would help bring down Assad and prevent an even lengthier conflict.

"Can we make the situation better if we get involved and therefore reduce some of the downside risk? I would say yes," said Stephen Hadley, national security adviser to former President George W. Bush.

"Waiting and letting this go longer is not going to make it less of a mess, it's going to make it more of a mess," he said.

Concern that the humanitarian crisis will destabilize the broader region is also weighing on the international community. The United Nations has said about 170,000 people have fled Syria as a result of the fighting.

Equally worrisome is the threat of a drawn-out Syrian civil war.

"We have this physical imagery of civil wars spilling across boundaries, it sort of appeals to our sense of how nasty things spill, like coffee on the kitchen table," said Paul Pillar, a former CIA analyst who is now a Georgetown University professor.

"I frankly don't worry about that nearly as much as just a prolonged conflict inside Syria," Pillar said.